1. Field of the Invention
This invention relates generally to an air blast apparatus, and more particularly to an air blast apparatus for yarn drawing machines in which the blast effects are enhanced.
2. Description of the Prior Art
FIG. 1 illustrates a conventional air blast apparatus 10 used in yarn drawing machines. It comprises a tubular guide pipe 11 which has a peripheral wall provided with a throat portion 111. A blast nozzle 12 having a blast outlet 121 extends from a front end of the throat portion 111. High pressure introduced from two ends 112 of the guide pipe 11 blows out from both side sections 122 of the blast outlet 121 and does not reach the middle section 123 of the pipe. In order that the draft blows out from the whole length of the blast outlet 121, the draft pressure has to be increased. However, there will still be high pressure at both side sections 122 and low pressure at the middle section 123.